Low latency physical uplink control channel with scheduling request and channel state information

ABSTRACT

Methods, systems, and devices for wireless communication are described. A user equipment (UE) and a base station may use low latency communications to improve the throughput of a wireless link. To facilitate efficient low latency communication, the UE may send UE-initiated CSI reports in addition to periodic and base station-initiated reports. For example, the UE may, in various examples, send UE-initiated CSI reports using contention based spectrum, using a request-to-transmit, or using a CSI differential (i.e., an indicator of a change in channel conditions). The base station may schedule different UEs for uplink low latency communication by providing resources to each UE for CSI and scheduling requests (SRs) using coherent or non-coherent uplink transmissions. The CSI and SR may also be combined with uplink feedback.

CROSS REFERENCES

The present application for patent claims priority to U.S. ProvisionalPatent Application No. 62/190,506 entitled “Low Latency Physical UplinkControl Channel with Scheduling Request and Channel State Information,”filed Jul. 9, 2015, assigned to the assignee hereof.

BACKGROUND

The following relates generally to wireless communication, and morespecifically to low latency physical uplink control channel (PUCCH) withscheduling requests (SR) and channel state information (CSI).

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, and orthogonal frequencydivision multiple access (OFDMA) systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example telecommunication standardis Long Term Evolution (LTE). LTE is designed to improve spectralefficiency, lower costs, improve services, make use of new spectrum, andbetter integrate with other open standards. LTE may use OFDMA on thedownlink (DL), single-carrier frequency division multiple access(SC-FDMA) on the uplink (UL), and multiple-input multiple-output (MIMO)antenna technology. A wireless multiple-access communications system(including an LTE system) may include a number of base stations, eachsupporting communication for multiple communication devices, which mayotherwise be known as user equipment (UE).

In some cases, a base station may transmit reference signals to a UE toaid in evaluating channel conditions. The UE may then send channel stateinformation (CSI) reports to the base station periodically or wheninitiated by the base station. Periodic and base station-initiated CSIreports may be sufficient to determine current channel conditions. Ifthe system supports low latency communications, however, the periodicand base station-initiated reports may be insufficient. This may resultin dropped packets and delayed communications.

SUMMARY

To facilitate efficient low latency communication between a userequipment (UE) and a base station, the UE may send UE-initiated channelstate information (CSI) reports, which may be in addition to periodicand base station-triggered reports. For example, the UE may sendUE-initiated CSI reports using contention-based spectrum, using arequest-to-transmit, using a CSI differential (i.e., an indicator of achange in channel conditions), and the like. In some cases, the basestation may schedule different UEs for uplink low latency communicationby providing resources to each UE for CSI and scheduling requests (SRs)using coherent or non-coherent uplink transmissions. The CSI and SR maybe combined with uplink feedback, including, for instance, hybridautomatic repeat request (HARQ) feedback. The uplink resources forUE-initiated CSI reporting may include and may be selected fromdifferent time resources, subcarriers, or different cyclic shifts of apredetermined sequence.

A method of wireless communication is described. The method may includedetermining CSI for a communication link that uses a first TTI durationin a system that supports operation with the first TTI duration and asecond TTI duration that is greater than the first TTI duration. Themethod may also include identifying resources of an unscheduled uplinkchannel on which to transmit a report with the determined CSI andtransmitting the report on the identified resources.

An apparatus for wireless communication is described. The apparatus mayinclude means for determining CSI for a communication link that uses afirst TTI duration in a system that supports operation with the firstTTI duration and a second TTI duration that is greater than the firstTTI duration. The apparatus may also include means for identifyingresources of an unscheduled uplink channel on which to transmit a reportwith the determined CSI, and means for transmitting the report on theidentified resources.

A further apparatus for wireless communication is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be operable, when executed by the processor, to causethe apparatus to determine CSI for a communication link that uses afirst TTI duration in a system that supports operation with the firstTTI duration and a second TTI duration that is greater than the firstTTI duration, identify resources of an unscheduled uplink channel onwhich to transmit a report with the determined CSI, and transmit thereport on the identified resources.

A non-transitory computer-readable medium storing code for wirelesscommunication is described. The code may include instructions executableto determine CSI for a communication link that uses a first TTI durationin a system that supports operation with the first TTI duration and asecond TTI duration that is greater than the first TTI duration,identify resources of an unscheduled uplink channel on which to transmita report with the determined CSI, and transmit the report on theidentified resources.

Some examples of the method, apparatus, or non-transitorycomputer-readable media described above may include features, steps,means, or instructions for selecting the resources from a set ofresources reserved for uplink control information (UCI). Some examplesmay include receiving signaling that indicates the set of resourcesreserved for UCI. In some examples, the signaling is or includes adownlink grant.

In some examples of the method, apparatus, or non-transitorycomputer-readable media described above, the set of resources reservedfor UCI includes resources reserved for a scheduling request (SR), a CSIreport, or hybrid automatic repeat request (HARQ) feedback, or anycombination thereof. In some examples, the set of resources reserved forUCI is or includes a set of resource blocks of a TTI having the firstTTI duration. Additionally or alternatively, the set of resourcesreserved for UCI may be based at least in part on a number of userequipment (UEs) for which the set of resources reserved for UCI isallocated, and the number of UEs may include coherent users ornon-coherent users, or both.

Some examples of the method, apparatus, or non-transitorycomputer-readable media described above may include features, steps,means, or instructions for determining that a TTI having the first TTIduration is available for CSI reporting. In some examples, the report istransmitted with a different cyclic shift from an uplink referencesignal.

Another method of wireless communication is described. The method mayinclude determining CSI for a communication link that uses a first TTIduration in a system that supports operation with the first TTI durationand a second TTI duration that is greater than the first TTI duration.The method may also include transmitting a request for resources onwhich to send a report with the determined CSI and receiving a grant foruplink resources for the report in response to the request, andtransmitting the report using the uplink resources.

Another apparatus for wireless communication is described. The apparatusmay include means for determining CSI for a communication link that usesa first TTI duration in a system that supports operation with the firstTTI duration and a second TTI duration that is greater than the firstTTI duration. The apparatus may also include means for transmitting arequest for resources on which to send a report with the determined CSI,means for receiving a grant for uplink resources for the report inresponse to the request, and means for transmitting the report using theuplink resources.

A further apparatus for wireless communication is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be operable, when executed by the processor, to causethe apparatus to determine CSI for a communication link that uses afirst TTI duration in a system that supports operation with the firstTTI duration and a second TTI duration that is greater than the firstTTI duration, transmit a request for resources on which to send a reportwith the determined CSI, receive a grant for uplink resources for thereport in response to the request, and transmit the report using theuplink resources.

Another non-transitory computer-readable medium storing code forwireless communication is described. The code may include instructionsexecutable to determine CSI for a communication link that uses a firstTTI duration in a system that supports operation with the first TTIduration and a second TTI duration that is greater than the first TTIduration, transmit a request for resources on which to send a reportwith the determined CSI, receive a grant for uplink resources for thereport in response to the request, and transmit the report using theuplink resources.

Another method of wireless communication is described. The method mayinclude transmitting a report with CSI for a communication link thatuses a first TTI duration in a system that supports operation with thefirst TTI duration and a second TTI duration that is greater than thefirst TTI duration. The method may also include determining a change ina channel state for the communication link and transmitting signalingthat indicates a difference between the reported CSI and the change inthe channel state.

A further apparatus for wireless communication is described. Theapparatus may include means for transmitting a report with CSI for acommunication link that uses a first TTI duration in a system thatsupports operation with the first TTI duration and a second TTI durationthat is greater than the first. The apparatus may also include means fordetermining a change in a channel state for the communication link andmeans for transmitting signaling that indicates a difference between thereported CSI and the change in the channel state.

A further apparatus for wireless communication is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be operable, when executed by the processor, to causethe apparatus to transmit a report with CSI for a communication linkthat uses a first TTI duration in a system that supports operation withthe first TTI duration and a second TTI duration that is greater thanthe first, determine a change in a channel state for the communicationlink, and transmit signaling that indicates a difference between thereported CSI and the change in the channel state.

Another non-transitory computer-readable medium storing code forwireless communication is described. The code may include instructionsexecutable to transmit a report with CSI for a communication link thatuses a first TTI duration in a system that supports operation with thefirst TTI duration and a second TTI duration that is greater than thefirst TTI duration, determine a change in a channel state for thecommunication link, and transmit signaling that indicates a differencebetween the reported CSI and the change in the channel state.

In some examples of the method, apparatus, or non-transitorycomputer-readable media described above, the report with the CSI or thesignaling that indicates the difference between the CSI and the changein the channel state is transmitted on resources selected from a set ofresources reserved for uplink control information (UCI). In someexamples, the set of resources reserved for UCI includes resourcesreserved for scheduling request (SR), CSI reports, hybrid automaticrepeat request (HARQ) feedback, or any combination thereof. Additionallyor alternatively, the set of resources reserved for UCI may be reservedbased at least in part on a number of user equipment (UEs) for which theset of resources reserved for UCI is allocated, and the number of UEscomprises coherent users or non-coherent users, or both.

Some examples of the method, apparatus, or non-transitorycomputer-readable media described above may include features, steps,means, or instructions for receiving a grant for resources on which tosend the report with the CSI or the signaling that indicates thedifference between the CSI and the change in the channel state in adownlink data channel. In some examples, the report with the CSI or thesignaling that indicates the difference between the CSI and the changein the channel state is transmitted with a different cyclic shift froman uplink reference signal.

A method of wireless communication is described. The method may includedetermining a set of resources reserved for UCI. The method may alsoinclude receiving at least one of a report with CSI, a request forresources on which to send a CSI report, or signaling that indicates achange in CSI on resources of the set of reserved resources from a UE,the communicating using a first TTI duration in a system that supportsoperation with the first TTI duration and a second TTI duration that isgreater than the first.

An apparatus for wireless communication is described. The apparatus mayinclude means for determining a set of resources reserved for UCI. Theapparatus may also include means for receiving at least one of a reportwith CSI, a request for resources on which to send a CSI report, orsignaling that indicates a change in CSI on resources of the set ofreserved resources from a UE, the communicating using a first TTIduration in a system that supports operation with the first TTI durationand a second TTI duration that is greater than the first.

A further apparatus for wireless communication is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory and operable,when executed by the processor, to cause the apparatus to determine aset of resources reserved for UCI and receive at least one of a reportwith CSI, a request for resources on which to send a CSI report, orsignaling that indicates a change in CSI on resources of the set ofreserved resources from a UE, the communicating using a first TTIduration in a system that supports operation with the first TTI durationand a second TTI duration that is greater than the first.

A non-transitory computer-readable medium storing code for wirelesscommunication is described. The code may include instructions executableto determine a set of resources reserved for UCI, and receive at leastone of a report with CSI, a request for resources on which to send a CSIreport, or signaling that indicates a change in CSI on resources of theset of reserved resources from a UE, the communicating using a first TTIduration in a system that supports operation with the first TTI durationand a second TTI duration that is greater than the first.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the disclosure are described in reference to the followingfigures:

FIG. 1 illustrates an example of a wireless communications system thatsupports low latency physical uplink control channel (PUCCH) withscheduling request (SR) and channel state information (CSI) inaccordance with various aspects of the present disclosure;

FIG. 2 illustrates an example of a wireless communications system thatsupports low latency PUCCH with SR and CSI in accordance with variousaspects of the present disclosure;

FIGS. 3A and 3B illustrate examples of coherent SR/CSI scheduling andnon-coherent SR/CSI scheduling within a system that supports low latencyPUCCH with SR and CSI in accordance with various aspects of the presentdisclosure;

FIGS. 4-6 depict process flow diagrams that illustrate communicationwithin a system that supports low latency PUCCH with SR and CSI inaccordance with various aspects of the present disclosure;

FIGS. 7-9 show block diagrams of a wireless device or devices thatsupport low latency PUCCH with SR and CSI in accordance with variousaspects of the present disclosure;

FIG. 10 illustrates a block diagram of a system, including a userequipment (UE), that supports low latency PUCCH with SR and CSI inaccordance with various aspects of the present disclosure;

FIGS. 11-13 show block diagrams of a wireless device or devices thatsupport low latency PUCCH with SR and CSI in accordance with variousaspects of the present disclosure;

FIG. 14 illustrates a block diagram of a system, including a basestation, that supports low latency PUCCH with SR and CSI in accordancewith various aspects of the present disclosure; and

FIGS. 15-20 illustrate methods for low latency PUCCH with SR and CSI inaccordance with various aspects of the present disclosure.

DETAILED DESCRIPTION

A wireless system may support both uplink and downlink transmissionsbetween a user equipment (UE) and a base station. In some cases, bothuplink and downlink transmissions may be based on low latency operations(e.g., operations where the basic time unit for scheduling is less than1 ms). To facilitate efficient low latency communication, the timing fora channel state information (CSI) report to a base station may beinitiated by a UE.

CSI may be determined by a UE based on reference signals transmitted bythe base station. In addition to UE-initiated CSI reporting, CSI reportsmay be scheduled periodically or initiated by the base station. Latencytolerant traffic may be effectively communicated or monitored usingperiodic or base station-initiated reporting. For low latency operation,UE-initiated CSI reports may be used to ensure that transmissions arebased on current CSI. UE-initiated CSI reports may be sent in severalways. For example, a UE may transmit CSI reports using contention-baseduplink resources, or it may send a CSI Request-to-Transmit (e.g., a1-bit indicator), or it may transmit a differential CSI (which also maybe a 1-bit indicator). UEs may also transmit uplink control informationthat includes scheduling request (SR) messages, and feedback fordownlink transmissions (e.g., acknowledgements (ACKs) or negativeacknowledgements (NACKs)). In some cases, UE-initiated CSI reports maybe combined with SR transmissions.

In some examples, a two symbol low latency transmission time interval(TTI) structure may be used, and low latency users may be assigned to anSR/CSI resource pool. Coherent or non-coherent transmission may be used.Pilot signals (for coherent transmissions), feedback and SR/CSI requestsmay be sent using separate cyclic shifts of a predetermined uplinksequence.

Some users may access a system or transmit initial uplink messages usinglonger TTIs—that is, some users send initial uplink transmissions thatare not associated with low latency operation. So a user may use aphysical random access channel (PRACH) to obtain a low latency uplinkresource. The PRACH signature may be confined to a set of signaturesthat may be mapped to low latency SR/CSI requests. A base station mayhandle PRACH to obtain a low latency uplink resource in various ways.For example, the base station may grant one time access for SR/CSIrequests through a PRACH response. Or the base station may set asideadditional PUCCH resources. In some cases, the base station reassigns auser with resources previously assigned to another existing user. It isthus possible for the base station to indicate to the existing user aloss of resources and convey resources to the new user through a PRACHconfiguration.

Aspects of the disclosure introduced above are further described belowin the context of a wireless communication system. Specific examples arethen described for coherent and non-coherent SR/CSI reports, andalternatives for UE-initiated CSI reporting are discussed. These andother aspects of the disclosure are further illustrated by and describedwith reference to apparatus diagrams, system diagrams, and flowchartsthat relate to low latency physical uplink control channel (PUCCH) withscheduling request (SR) and channel state information (CSI).

FIG. 1 illustrates an example of a wireless communications system 100 inaccordance with various aspects of the present disclosure. The wirelesscommunications system 100 includes base stations 105, user equipment(UEs) 115, and a core network 130. In some examples, the wirelesscommunications system 100 may be a Long Term Evolution(LTE)/LTE-Advanced (LTE-A) network. Wireless communication may supportlow latency communications between a UE 115 and base station 105. Thismay include UE-initiated CSI reports.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Each base station 105 may providecommunication coverage for a respective geographic coverage area 110.Communication links 125 shown in wireless communications system 100 mayinclude uplink (UL) transmissions from a UE 115 to a base station 105,or downlink (DL) transmissions, from a base station 105 to a UE 115. UEs115 may be dispersed throughout the wireless communications system 100,and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to as a mobile station, a subscriber station, a remote unit, awireless device, an access terminal, a handset, a user agent, a client,or some other suitable terminology. A UE 115 may also be a cellularphone, a wireless modem, a handheld device, a personal computer, atablet, a personal electronic device, a machine type communication (MTC)device or the like.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., S1, etc.). Base stations105 may communicate with one another over backhaul links 134 (e.g., X2,etc.) either directly or indirectly (e.g., through core network 130).Base stations 105 may perform radio configuration and scheduling forcommunication with UEs 115, or may operate under the control of a basestation controller (not shown). In some examples, base stations 105 maybe macro cells, small cells, hot spots, or the like. Base stations 105may also be referred to as eNodeBs (eNBs) 105. As described herein, basestations 105 may receive CSI reports from UEs 115 on resourcesdesignated or reserved for uplink control information.

A frame structure may be used to organize physical resources. A framemay be a 10 ms interval that may be further divided into 10 equallysized sub-frames. Each sub-frame may include two consecutive time slots.Each slot may include 6 or 7 orthogonal frequency division multipleaccess (OFDMA) symbol periods. In some cases, a subframe may be thebasic unit of scheduling, known as the transmission time interval (TTI).In other cases, such as with low latency operation, a different TTI maybe used, such as a symbol period, a pair of symbol periods, or a slot.TTIs for low latency operation may thus have a numerology that iscompatible with other LTE transmission structures and timing (e.g.,subframe). The system 100 may concurrently support communication usingTTIs over different duration (e.g., TTIs having a duration of a subframeand TTIs having a duration of a symbol period or a slot).

In some cases, wireless communications system 100 may utilize one ormore enhanced component carriers (eCCs). An enhanced component carrier(eCC) may be characterized by one or more features including: flexiblebandwidth, different TTIs, and modified control channel configuration.In some cases, an eCC may be associated with a carrier aggregation (CA)configuration or a dual connectivity configuration (e.g., when multipleserving cells have a suboptimal backhaul link). An eCC may also beconfigured for use in unlicensed spectrum or shared spectrum (e.g.,where more than one operator is licensed to use the spectrum). An eCCcharacterized by flexible bandwidth may include one or more segmentsthat may be utilized by UEs 115 that do are not capable of monitoringthe whole bandwidth or prefer to use a limited bandwidth (e.g., toconserve power).

A resource element consists of one symbol period and one subcarrier (a15 KHz frequency range). A resource block may contain 12 consecutivesubcarriers in the frequency domain and, for a normal cyclic prefix ineach OFDM symbol, 7 consecutive OFDM symbols in the time domain (1slot), or 84 resource elements. Some resource elements may includedownlink (DL) reference signals (DL-RS). The DL-RS may include acell-specific reference signals (CRS) and a UE-specific RS (UE-RS),which may also be referred to as demodulation references signals (DMRS).UE-RS may be transmitted on the resource blocks associated with physicaldownlink shared channel (PDSCH). References signals may be employed asdiscussed below. The number of bits carried by each resource element maydepend on the modulation scheme (the configuration of symbols that maybe selected during each symbol period). Thus, the more resource blocksthat a UE receives and the higher the modulation scheme, the higher thedata rate may be.

PUCCH may be used for uplink (UL) acknowledgements (ACKs), schedulingrequests (SRs) and channel quality indicators (CQI) and other UL controlinformation. A PUCCH may be mapped to a control channel defined by acode and two consecutive resource blocks. UL control signaling maydepend on the presence of timing synchronization for a cell. PUCCHresources for SR and CSI reporting may be assigned (and revoked) throughRRC signaling. In some cases, resources for SR may be assigned afteracquiring synchronization through a RACH procedure. In other cases, anSR may not be assigned to a UE 115 through the RACH (i.e., synchronizedUEs may or may not have a dedicated SR channel). PUCCH resources for SRand CSI may be lost when the UE is no longer synchronized. In somecases, CSI may be periodic or triggered by the base station 105. Inother cases, such as with low latency operation, CQI may be initiated bya UE 115.

A base station 105 may insert periodic pilot symbols such as CRS to aidUEs 115 in channel estimation and coherent demodulation. CRS may includeone of 504 different cell identities. They may be modulated usingquadrature phase shift keying (QPSK) and power boosted (e.g.,transmitted at 6 dB higher than the surrounding data elements) to makethem resilient to noise and interference. CRS may be embedded in 4 to 16resource elements in each resource block based on the number of antennaports or layers (up to 4) of the receiving UEs 115. In addition to CRS,which may be utilized by all UEs 115 in the geographic coverage area 110of the base station 105, DMRS may be directed toward specific UEs 115and may be transmitted on resource blocks assigned to those UEs 115.DMRS may include signals on 6 resource elements in each resource blockin which they are transmitted. The DMRS for different antenna ports mayeach utilize the same 6 resource elements, and may be distinguishedusing different orthogonal cover codes (e.g., masking each signal with adifferent combination of 1 or −1 in different resource elements). Insome cases, two sets of DMRS may be transmitted in adjoining resourceelements. In some cases, additional reference signals known as channelstate information reference signals (CSI-RS) may be included to aid ingenerating CSI. On the UL, a UE 115 may transmit a combination ofperiodic sounding reference signal (SRS) and UL DMRS for link adaptationand demodulation, respectively.

A base station 105 may gather CSI from a UE 115 in order to efficientlyconfigure and schedule the channel. This information may be sent fromthe UE 115 in the form of a channel state report. A channel state reportmay contain a rank indicator (RI) requesting a number of layers to beused for DL transmissions (e.g., based on the antenna ports of the UE115), a precoding matrix indicator (PMI) indicating a preference forwhich precoder matrix should be used (based on the number of layers),and a CQI representing the highest modulation and coding scheme (MCS)that may be used. CQI may be calculated by a UE 115 after receivingpredetermined pilot symbols such as CRS or CSI-RS. RI and PMI may beexcluded if the UE 115 does not support spatial multiplexing (or is notin support spatial mode). The type of information included in the reportdetermines a reporting type. CSI reports may be periodic or aperiodic.That is, a base station 105 may configure a UE 115 to send periodicreports at regular intervals, and may also request additional reports asneeded. Aperiodic reports may include wideband reports indicating thechannel quality across an entire cell bandwidth, UE selected reportsindicating a subset of the best subbands, or configured reports in whichthe subbands reported are selected by the base station 105. In somecases, such as with low latency operation, the UE 115 may also sendreports of updates based on changing channel conditions. These reportsmay be referred to as UE-initiated CSI reports.

A UE 115 may transmit a RACH preamble to a base station 105 to establisha new connection or to initiate low latency communications. This may beknown as RACH message 1. For example, the RACH preamble may be randomlyselected from a set of 64 predetermined sequences. This may enable thebase station 105 to distinguish between multiple UEs 115 trying toaccess the system simultaneously. The base station 105 may respond witha random access response (RAR), or RACH message 2, that provides anuplink (UL) resource grant, a timing advance, and a temporary cell radionetwork temporary identity (C-RNTI). The UE 115 may then transmit aradio resource control (RRC) connection request, or RACH message 3,along with a temporary mobile subscriber identity (TMSI) (if the UE 115has previously been connected to the same wireless network) or a randomidentifier. The RRC connection request may also indicate the reason theUE 115 is connecting to the network (e.g., emergency, signaling, dataexchange, etc.). The base station 105 may respond to the connectionrequest with a contention resolution message, or RACH message 4,addressed to the UE 115, which may provide a new cell radio networktemporary identity (C-RNTI). If the UE 115 receives a contentionresolution message with the correct identification, it may proceed withRRC setup. If the UE 115 does not receive a contention resolutionmessage (e.g., if there is a conflict with another UE 115) it may repeatthe RACH process by transmitting a new RACH preamble.

A UE 115 and a base station 105 may use low latency communications toimprove the throughput of a wireless link. To facilitate efficient lowlatency communication the UE 115 may send UE-initiated CSI reports,which may be in addition to periodic and base station triggered reports.For example, the UE 115 may send UE-initiated CSI reports usingcontention based spectrum, using a request-to-transmit, or using a CSIdifferential (i.e., an indicator of a change in channel conditions). Thebase station 105 may schedule different UEs 115 for uplink low latencycommunication by providing resources to each UE 115 for CSI and SRsusing coherent or non-coherent uplink transmissions. The CSI and SR mayalso be combined with uplink feedback based on downlink transmissions.The uplink resources may be based on different time resources,subcarriers, or different cyclic shifts of a predetermined sequence.

FIG. 2 illustrates an example of a wireless communications system 200for low latency PUCCH with SR and CSI in accordance with various aspectsof the present disclosure. Wireless communications system 200 mayinclude UEs 115-a, 115-b, 115-c and base station 105-a, which may beexamples of a UE 115 base station 105 described with reference toFIG. 1. Wireless communications system 200 may support both uplink anddownlink transmissions between UEs 115-a, 115-b, 115-c and base station105-a. Transmissions in each direction may be either data or controlmessages. Uplink control information may include CQI, SR messages, andfeedback for downlink transmissions (e.g., AKCs or NACKs). In somecases, both uplink and downlink transmissions may be based on lowlatency operations (e.g., operations where the basic time unit forscheduling is less than 1 ms).

CQI may reflect CSI determined by UE 115-a (or another UE 115) based onreference signals transmitted by base station 105-a. CQI may bescheduled periodically, or initiated by base station 105-a. For lowlatency operation, UE-initiated CSI reports may also be used to ensurethat transmissions are based on current CSI. UE-initiated CSI reportsmay be sent in several ways. For example, a UE 115-a may transmit CSIreports based on contention based uplink resources, it may send a CSIrequest-to-transmit (e.g., a 1-bit indicator), or it may transmit adifferential CSI (which also may be a 1-bit indicator). In some cases,UE-initiated CSI reports may be combined with SR transmissions.

In some examples, CSI reports may be allocated through contention-baseduplink resources. So resource elements may be pre-allocated for controlinformation transmission. Users that attempt to transmit may randomlychoose uplink resources to send control information. Although, in somecases, contention-based schemes with large payload sizes may be costlydue to either over-allocation of resources or latency penalties createdby collisions.

In other examples, a one bit CSI request-to-transmit message orindication may be sent from UE 115-a to base station 105-a on an uplinktransmission. Upon receiving the request, base station 105-a maytransmit a downlink grant to specify a CSI trigger with pre-allocateduplink resources. The base station 105-a may additionally couple uplinkCSI transmissions with uplink group ACK and a CRC. The one bittransmission may be pre-allocated for a given low latency user.

In other examples, UE 115-a may generate a one bit differential CSI fortransmission to base station 105-a. For instance, UE 115-a may send afull CSI report either through a periodic CSI allocation or an aperiodicallocation started by a trigger from the base station 105-a. UE 115-amay send a differential CSI value that accumulates on top of the fullCSI report. The one bit transmission may be pre-allocated for a givenlow latency user.

In some systems, including system 200 in some case, a two symbol lowlatency TTI structure may be used, and low latency users may be assignedin the SR/CSI resource pool. In one case, a coherent transmission may beused. The coherent transmission may allow three users per one half RB. Apilot signal and a SR/CSI request may be sent on two separate cyclicshifts. This may use the same structure as the previously definedcoherent ACK structure. Or a non-coherent transmission may be used. Forexample, the non-coherent transmission may enable six users per one halfRB. The SR/CSI request may thus be sent on a single cyclic shift. In anycase, capacity may be further improved if the SR/CSI resource pool isshared with ACK users or if users are assigned in both symbols of bothRBs. Base station 105-a may predefine per user which TTIs are assignedas an SR or as a CSI req. Thus, base station 105-a may multiplex uplinktransmissions from UEs 115-a, 115-b, 115-c.

In some examples, a two symbol low latency TTI structure may be used,and ACK/NACK resource pools may additionally be modified to includeSR/CSI. Users who are scheduled a low latency physical downlink sharedchannel (uPDSCH) assignment in downlink may be assigned an uplink ACKphysical uplink control channel (PUCCH) resource. On a frequency hoppedsymbol, users may use three cyclic shifts per RB. Pilot symbols may becoherently sent with ACK resources and SR/CSI request resources on eachof three cyclic shifts. Base station 105-a may predefine for each userwhich TTIs are assigned as RS requests or CSI requests.

The user capacity for a two symbol low latency TTI structure may bedetermined based on a number of RBs. For example, for N RBs, a total of2N symbol resources may be available. In this example, Y symbolresources may be used as ACK resources for 2Y users. If coherenttransmission is used, 2N−Y symbol resources may be used for SR/CSIrequest resources for 3·(2N−Y) users. If non-coherent transmission isused, 2N−Y symbols may be used as SR/CSI request resources for 6·(2N−Y)users. Coherent and non-coherent users may be combined in the same RB.To support even more users, users can be assigned to SR/CSI resourceswith a specific periodicity, but this may lead to increased latency.

Some users may not, due to system constraints, operating conditions, oruser preference, utilize low latency access to the uplink. So, asmentioned above, a user may use RACH to obtain a low latency uplinkresource. The RACH signature may be confined to a set of signatures thatmay be mapped to low latency SR/CSI requests. Base station 105-a mayhandle using RACH to obtain a low latency uplink resource in many ways.For example, base station 105-a may grant one time access for SR/CSIrequests through a RACH response. Base station 105-a may set asideadditional PUCCH resources. In other examples, base station 105-a mayswap the user with an existing user. Base station 105-a may thusindicate to the existing user a loss of resources and convey resourcesto the new user through a RACH configuration.

FIGS. 3A and 3B illustrates an example coherent SR/CSI schedulingconfiguration 301 and non-coherent SR/CSI scheduling configuration 302for low latency PUCCH with SR and CSI in accordance with various aspectsof the present disclosure. Coherent SR/CSI scheduling configuration 301and non-coherent SR/CSI scheduling configuration 302 may be utilized byUEs 115 and base stations 105 described with reference to FIGS. 1-2.Coherent SR/CSI scheduling configuration 301 and non-coherent SR/CSIscheduling configuration 302 may represent an example based on atwo-symbol TTI with frequency hopping; similar scheduling techniques maybe used for systems with different configuration (e.g., with other TTIlengths).

Symbols 305-b and 310-a of coherent SR/CSI scheduling configuration 301may include coherent transmissions, including a pilot symbol, a SR, anda CSI request for three different users. That is, the uplink resourcesfor each user may occupy 4 out of 12 resource units. Symbols 305-b and310-a may be utilized by the same users and transmitted at a differenttime. Symbol 305-b may be, for example, symbol 2n in a sequence ofsymbols. Symbol 310-a may be transmitted in a different frequency assymbol 305-b and may temporally follow symbol 305-b, i.e., symbol 2n+1.Symbols 305-b and 310-a may be coherent due to transmitting a pilotsymbol alongside an SR and CSI request.

Symbols 305-a and 310-b (and similarly, symbols 305-c and 310-d) may bescheduled together based on transmissions including a pilot symbol, anACK, a SR, and a CSI request for two users. That is, the subcarriers ofresource blocks 315 and the cyclic shifts of a predetermined signal mayrepresent a resource pool of 12 units. An uplink transmission includinga pilot symbol, an ACK, a SR, and a CSI request may use 6 units, so eachsymbol may accommodate 2 users. Symbol 305-a may be, for example, symbol2n in a sequence of symbols. Symbol 310-b may be transmitted in adifferent frequency as symbol 305-a and may temporally follow symbol305-a, i.e., symbol 2n+1.

Symbols 305-d and 310-c of non-coherent SR/CSI scheduling configuration302 may include non-coherent uplink SR/CSI transmissions for 6 differentusers (i.e., SR/CSI transmissions that are not accompanied by a pilotsignal). Each non-coherent SR/CSI transmission may utilize 2 resourceunits per resource block 315. Thus, 6 users may be simultaneouslymultiplexed. Symbol 305-d may represent a first symbol period on a firstresource block at symbol 2n and symbol 310-c may represent a subsequentsymbol 2n+1 on a different resource block 315 based on a frequencyhopping configuration.

Resource blocks 315-a and 315-b may be paired frequency regions (e.g.,based on a frequency hopping configuration) used to schedule uplinkinformation regarding multiple users, including pilot signals, ACKs,SRs, and CSI requests. Resource Block 315-a may be at a higher frequencythan resource block 315-b. The information transmitted by users inresource block 315-a during symbol 305-a (or 305-c) may be subsequentlytransmitted during symbol 310-b (or 310-d) using resource block 315-bafter transmitting, and the information in resource block 315-b may hopfrequencies to the frequency of resource block 315-a.

Transmissions 320-a, 320-b, 320-c, and 320-d may represent coherenttransmissions including a pilot symbol, an ACK, a SR, and a CSI request.Transmissions 320-a, 320-b, 320-c, and 320-d may each includeinformation from different UEs 115. Transmission 325-a, 325-b, and 325-cmay be transmissions including a pilot symbol, a SR, and a CSI request.Transmissions 325-a, 325-b, and 325-c may be coherent, as they include apilot signal along the SR and CSI request. These transmissions mayinclude information for different users, and each of them may be sent inthe same resource block 315-b.

Transmissions 330-a, 330-b, 330-c, 330-d, 330-e, and 330-f may betransmissions including, for example, a SR and a CSI request. Thesetransmissions may be non-coherent, as they may not include a pilotsignal along the SR and CSI request. These transmissions may includeinformation for different users, but each of them may be sent in thesame resource block 315-d. Similar to how symbols 305-a and 305-b wouldhop frequencies to become symbols 310-a and 310-b respectively,transmissions in resource block 315-d may hop frequencies to thefrequency of 315-c and vice versa for a temporally followingtransmission.

FIG. 4 illustrates an example of a process flow 400 in a system thatsupports low latency PUCCH with SR and CSI in accordance with variousaspects of the present disclosure. Process flow 400 may include a UE115-d and base station 105-b, which may be examples of a UE 115 and basestation 105 described with reference to FIGS. 1-2. Each of thesecomponents may be in communication with one another through a lowlatency wireless system. Process flow 400 may represent a method oftransmitting a UE-initiated CSI report using contention based (orunscheduled) resources.

In some cases a UE 115-a and base station 105 may operate in a shared orunlicensed frequency spectrum. These devices may perform a clear channelassessment (CCA) prior to communicating in order to determine whetherthe channel is available. A CCA may include an energy detectionprocedure to determine whether there are any other active transmissions.For example, the device may infer that a change in a signal strength ofa power meter indicates that a channel is occupied. Specifically, signalpower is that is concentrated in a certain bandwidth and exceeds apredetermined noise floor may indicate another wireless transmitter. ACCA may also include detection of specific sequences that indicate useof the channel. For example, another device may transmit a specificpreamble prior to transmitting a data sequence.

At step 405, UE 115-d and base station 105-b may establish a low latencylink between one another. This communication link may use a first TTIduration in a system that supports operation with the first TTI durationand a second TTI duration that is greater than the first. For example,the first TTI duration may be the duration of one LTE symbol period, theduration of two LTE symbol periods, or the duration of one LTE slot, invarious examples.

At step 410, base station 105-b may send a pilot signal to UE 115-d. Thepilot signal may be a known data pattern that is processed in a knownmanner to both base station 105-b and UE 115-d. UE 115-d may use thepilot signal as a reference, for example, for calculating the channelresponse.

At step 415, UE 115-d may determine the CSI for the connection betweenthe UE 115-d and the base station 105-b. UE 115-d may use the previouslyreceived pilot signal as a reference for calculating the CSI. The CSImay be used by the base station 105-b as an indicator for channelcorrection in the case of a noisy or poor signal.

At step 420, UE 115-d may transmit the CSI report to base station 105-busing a contention based resource. For example, UE 115-d may transmit aUE-initiated CSI report to base station 105-b using shared or unlicensedspectrum (in some cases, these reports may be sent as a supplement toperiodic reports sent using licensed spectrum). If the channel on whichUE 115-d intends to transmit is being used, UE 115-d may be delayed fromtransmission according to a clear channel assessment procedure.

FIG. 5 illustrates an example of a process flow 500 in a system thatsupports low latency PUCCH with SR and CSI in accordance with variousaspects of the present disclosure. Process flow 500 may include a UE115-e and base station 105-c, which may be examples of a UE 115 and basestation 105 described with reference to FIGS. 1-2. Each of thesecomponents may be in communication with one another in through a lowlatency wireless system. Process flow 500 may represent a method fortransmitting a UE-initiated CSI report using a CSI transmission request.

At step 505, UE 115-e and base station 105-c may establish a low latencylink between one another. This communication link may use a first TTIduration in a system that supports operation with the first TTI durationand a second TTI duration that is greater than the first. Afterestablishing the low latency link, base station 105-c may send a pilotsignal to UE 115-e at step 510. The pilot signal may be a known datapattern that is processed in a known manner to both base station 105-cand UE 115-e. UE 115-e may use the pilot signal as a reference, forexample, for calculating the channel response.

At step 515, UE 115-e may determine the CSI for the connection betweenthe UE 115-e and the base station 105-c. UE 115-e may use the previouslyreceived pilot signal as a reference for calculating the CSI. The CSImay be used by the base station 105-c as an indicator for channelcorrection in the case of noisy or poor signal. At step 520, UE 115-emay send an uplink transmit request to base station 105-c. The uplinktransmit request may be sent asking permission for the UE 115-e to send,for example, the CSI determined in step 515 using the pilot signaltransmitted in step 510. In some cases the transmit request may be a1-bit indicator included in an uplink transmission as described herein(e.g., using a multiplexing configuration described with reference toFIG. 3).

At step 525, base station 105-c may send a downlink grant to UE 115-e.The downlink grant may be in response to, for example, the transmitrequest sent in step 520. The downlink grant may give UE 115-epermission to send, for example, the CSI report determined in step 515.In some cases, the downlink grant may include a trigger for sending aCSI report.

At step 530, UE 115-e may identify a trigger for sending a CSI report.This may lead to UE 115-e transmitting the CSI report determined in step515 to base station 105-c. This may happen as a result of receiving thedownlink grant received by UE 115-e in step 525. Then, at step 535, UE115-e may transmit a CSI report to base station 105-c.

FIG. 6 illustrates an example of a process flow 600 for low latencyPUCCH with SR and CSI in accordance with various aspects of the presentdisclosure. Process flow 600 may include a UE 115-f and base station105-d, which may be examples of a UE 115 and base station 105 describedwith reference to FIGS. 1-2. Process flow 600 may represent a method oftransmitting a UE-initiated CSI report as a differential based on abaseline established by a previously reported CSI.

UE 115-f and base station 105-d may establish a low latency link asshown in step 605. The low latency communication link may use a firstTTI duration in a system that supports operation with the first TTIduration and a second TTI duration that may be greater than the first.

At step 610, base station 105-d may send a pilot signal to UE 115-facross the low latency link established in step 605. The pilot signalmay be a known data pattern that is processed in a known manner to bothbase station 105-d and UE 115-f. UE 115-f may use the pilot signal as areference, for example, for calculating the channel response.

At step 615, UE 115-f may determine a first CSI based on, for example,the pilot signal sent in step 610. This CSI may be used as a referencefor future channel responses in determining if the quality of the lowlatency link is improving or getting worse. At step 620, UE 115-f maytransmit the CSI report to base station 105-d.

At step 625, base station 105-d may send another pilot signal. Thispilot signal may be a known pattern that is processed in a known mannerto both base station 105-d and UE 115-f. UE 115-f may use the pilotsignal as a reference, for example, for calculating the channelresponse. UE 115-f may then use the pilot signal to determine a CSIdifferential in step 630. The CSI differential may not be a full CSIreport, but instead may be a reference as to whether channel conditionshave improved or gotten worse since the previous pilot signaltransmission. UE 115 may then report the CSI differential to basestation 105-d, for example, across the low latency link established instep 605.

At step 635, UE 115-f may transmit the UE-initiated CSI differential(e.g., in a 1-bit field of an uplink transmission).

FIG. 7 shows a block diagram of a wireless device 700 that supports lowlatency PUCCH with SR and CSI in accordance with various aspects of thepresent disclosure. Wireless device 700 may be an example of aspects ofa UE 115 described with reference to FIGS. 1-6. Wireless device 700 mayinclude a receiver 705, a low latency CSI module 710, or a transmitter715. Wireless device 700 may also include a processor. Each of thesecomponents may be in communication with one another.

The receiver 705 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to low latencyPUCCH with SR and CSI, etc.). Information may be passed on to the lowlatency CSI module 710, and to other components of wireless device 700.In some examples, the receiver 705 may receive signaling that indicatesthe set of reserved resources. In some examples, the signaling includesa downlink grant.

The low latency CSI module 710 may determine CSI for a communicationlink that uses a first TTI duration in a system that supports operationwith the first TTI duration and a second TTI duration that is greaterthan the first, identify resources of an unscheduled uplink channel onwhich to transmit a report with the determined CSI, and transmit thereport on the identified resources.

The transmitter 715 may transmit signals received from other componentsof wireless device 700. In some examples, the transmitter 715 may becollocated with the receiver 705 in a transceiver. The transmitter 715may include a single antenna, or it may include a plurality of antennas.

FIG. 8 shows a block diagram of a wireless device 800 that supports lowlatency PUCCH with SR and CSI in accordance with various aspects of thepresent disclosure. Wireless device 800 may be an example of aspects ofa wireless device 700 or a UE 115 described with reference to FIGS. 1-7.Wireless device 800 may include a receiver 705-a, a low latency CSImodule 710-a, or a transmitter 715-a. Wireless device 800 may alsoinclude a processor. Each of these components may be in communicationwith one another. The low latency CSI module 710-a may also include aCSI identification module 805, a resource identification module 810, anda CSI reporting module 815.

The receiver 705-a may receive information which may be passed on to lowlatency CSI module 710-a, and to other components of wireless device800. The low latency CSI module 710-a may perform the operationsdescribed with reference to FIG. 7. The transmitter 715-a may transmitsignals received from other components of wireless device 800.

The CSI identification module 805 may determine CSI for a communicationlink that uses a first TTI duration in a system that supports operationwith the first TTI duration and a second TTI duration that is greaterthan the first as described with reference to FIGS. 2-6. The CSIidentification module 805 may also determine CSI for a communicationlink that uses a first TTI duration in a system that supports operationwith the first TTI duration and a second TTI duration that is greaterthan the first.

The resource identification module 810 may identify resources of anunscheduled uplink channel on which to transmit a report with thedetermined CSI as described with reference to FIGS. 2-6. In someexamples, identifying the resources of the unscheduled uplink channelincludes selecting the resources from a set of resources reserved forUCI. The set of reserved resources may include resources reserved for anSR, the CSI report, or HARQ feedback, or the like. In some examples, theset of reserved resources includes a set of resource blocks of a TTIhaving the first TTI duration. The set of reserved resources may bebased on a number of UEs for which the set of reserved resources may beallocated. The number of UEs, in turn, may include coherent users ornon-coherent users, or both. In some examples, the set of reservedresources may be periodically allocated to different UEs within thesystem. Additionally or alternatively, identifying the resources of theunscheduled uplink channel may include determining that a TTI having thefirst TTI duration is available for CSI reporting.

The CSI reporting module 815 may transmit the report on the identifiedresources as described with reference to FIGS. 2-6. In some examples,the report may be transmitted with a different cyclic shift from anuplink reference signal. The CSI reporting module 815 may also transmita report with CSI for a communication link that uses a first TTIduration in a system that supports operation with the first TTI durationand a second TTI duration that is greater than the first.

FIG. 9 shows a block diagram 900 of a low latency CSI module 710-b whichmay be a component of a wireless device 700 or a wireless device 800that supports low latency PUCCH with SR and CSI in accordance withvarious aspects of the present disclosure. The low latency CSI module710-b may be an example of aspects of a low latency CSI module 710described with reference to FIGS. 7-8. The low latency CSI module 710-bmay include a CSI identification module 805-a, a resource identificationmodule 810-a, and a CSI reporting module 815-a. Each of these modulesmay perform the functions described with reference to FIG. 8. The lowlatency CSI module 710-b may also include a RACH module 905, a resourcerequest module 910, a resource grant module 915, a channel statedifference module 920, and a difference reporting module 925.

The RACH module 905 may transmit a RACH message as described withreference to FIGS. 2-6. The RACH module 905 may also receive a messageresponsive to the RACH message, such that the resources of anunscheduled uplink channel are identified based on the responsivemessage. The RACH module 905 may also receive a message responsive tothe RACH message, such that the responsive message may include a grantfor uplink resources on which to transmit the report with the CSI or thesignaling that indicates the difference between the reported CSI and thechange in the channel state.

The resource request module 910 may transmit a request for resources onwhich to send a report with the determined CSI as described withreference to FIGS. 2-6.

The resource grant module 915 may receive a grant for uplink resourcesfor the report in response to the request as described with reference toFIGS. 2-6. In some examples, the uplink resources are selected from aset of resources reserved for UCI. In some examples, the set of reservedresources includes resources reserved for SR, CSI reports, and/or HARQfeedback. The set of reserved resources may be reserved based on anumber of UEs for which the set of reserved resources may be allocated,and the number of UEs may include coherent users or non-coherent users,or both. In some examples, the grant for uplink resources is received ina downlink data channel. The resource grant module 915 may receive agrant for resources on which to send the report with the CSI or thesignaling that indicates the difference between the reported CSI and thechange in the channel state in a downlink data channel.

The channel state difference module 920 may determine a change in achannel state for the communication link as described with reference toFIGS. 2-6.

The difference reporting module 925 may transmit signaling thatindicates a difference between the reported CSI and the change in thechannel state as described with reference to FIGS. 2-6. In someexamples, the report with the CSI or the signaling that indicates thedifference between reported CSI and the change in the channel state maybe transmitted on resources selected from a set of resources reservedfor UCI. In some examples, the set of reserved resources includesresources reserved for SR, CSI reports, HARQ feedback, or the like. Insome examples, the set of reserved resources is reserved based on anumber of UEs for which the set of reserved resources is allocated. Thenumber of UEs may include either or both coherent users or non-coherentusers. In some examples, the report with the CSI or the signaling thatindicates the difference between the reported CSI and the change in thechannel state are with a different cyclic shift from an uplink referencesignal.

FIG. 10 shows a diagram of a system 1000, including a UE, that supportslow latency PUCCH with SR and CSI in accordance with various aspects ofthe present disclosure. System 1000 may include UE 115-g, which may bean example of a wireless device 700, a wireless device 800, or a UE 115described with reference to FIGS. 1, 2 and 7-9. UE 115-g may include alow latency CSI module 1010, which may be an example of a low latencyCSI module 710 described with reference to FIGS. 7-9. UE 115-g may alsoinclude an ECC Module 1025 that may enable ECC operations as describedherein. UE 115-g may also include components for bi-directional voiceand data communications including components for transmittingcommunications and components for receiving communications. For example,UE 115-g may communicate bi-directionally with base station 105-e.

UE 115-g may also include a processor 1005, and memory 1015 (includingsoftware (SW) 1020), a transceiver 1035, and one or more antenna(s)1040, each of which may communicate, directly or indirectly, with oneanother (e.g., via buses 1045). The transceiver 1035 may, in combinationwith the low latency CSI module 1010, communicate bi-directionally, viathe antenna(s) 1040 or wired or wireless links, with one or morenetworks, as described above. For example, the transceiver 1035 maycommunicate bi-directionally with a base station 105 or another UE 115.The transceiver 1035 may include a modem to modulate the packets andprovide the modulated packets to the antenna(s) 1040 for transmission,and to demodulate packets received from the antenna(s) 1040.

The memory 1015 may include random access memory (RAM) and read onlymemory (ROM). The memory 1015 may store computer-readable,computer-executable software/firmware code 1020 including instructionsthat, when executed, cause the processor 1005 to perform variousfunctions described herein (e.g., low latency PUCCH with SR and CSI,etc.), including the functions described with reference to the lowlatency CSI module 1010 or the eCC module 1025, or both. Alternatively,the software/firmware code 1020 may not be directly executable by theprocessor 1005 but cause a computer (e.g., when compiled and executed)to perform functions described herein. The processor 1005 may include anintelligent hardware device, (e.g., a central processing unit (CPU), amicrocontroller, an application specific integrated circuit (ASIC),etc.).

FIG. 11 shows a block diagram of a wireless device 1100 that supportslow latency PUCCH with SR and CSI in accordance with various aspects ofthe present disclosure. Wireless device 1100 may be an example ofaspects of a base station 105 described with reference to FIGS. 1-10.Wireless device 1100 may include a receiver 1105, a base station lowlatency CSI module 1110, or a transmitter 1115. Wireless device 1100 mayalso include a processor. Each of these components may be incommunication with one another.

The receiver 1105 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to low latencyPUCCH with SR and CSI, etc.). Information may be passed on to the basestation low latency CSI module 1110, and to other components of wirelessdevice 1100.

The base station low latency CSI module 1110 may determine a set ofresources reserved for UCI, and receive at least one of a report withCSI, a request for resources on which to send a CSI report, or signalingthat indicates a change in CSI on resources of the set of reservedresources from a UE, the communicating using a first TTI duration in asystem that supports operation with the first TTI duration and a secondTTI duration that is greater than the first.

The transmitter 1115 may transmit signals received from other componentsof wireless device 1100. In some examples, the transmitter 1115 may becollocated with the receiver 1105 in a transceiver. The transmitter 1115may include a single antenna, or it may include a plurality of antennas.

FIG. 12 shows a block diagram of a wireless device 1200 that supportslow latency PUCCH with SR and CSI in accordance with various aspects ofthe present disclosure. Wireless device 1200 may be an example ofaspects of a wireless device 1100 or a base station 105 described withreference to FIGS. 1-11. Wireless device 1200 may include a receiver1105-a, a base station low latency CSI module 1110-a, or a transmitter1115-a. Wireless device 1200 may also include a processor. Each of thesecomponents may be in communication with one another. The base stationlow latency CSI module 1110-a may also include a UCI resourceidentification module 1205, and a CSI reception module 1210.

The receiver 1105-a may receive information which may be passed on tobase station low latency CSI module 1110-a, and to other components ofwireless device 1200. The base station low latency CSI module 1110-a mayperform the operations described with reference to FIG. 11. Thetransmitter 1115-a may transmit signals received from other componentsof wireless device 1200.

The UCI resource identification module 1205 may determine a set ofresources reserved for UCI as described with reference to FIGS. 2-6. Insome examples, the set of reserved resources includes resources reservedfor an SR, the CSI report, or HARQ feedback, or the like. The set ofreserved resources may include a set of resource blocks of a TTI havingthe first TTI duration. In some examples, the set of reserved resourcesmay be based on a number UEs for which the set of reserved resources maybe allocated, and the number of UEs may include coherent users ornon-coherent users, or both. The set of reserved resources may beperiodically allocated to different UEs within the system. The UCIresource identification module 1205 may also transmit to the UEsignaling indicating that a TTI having the first TTI duration isreserved for CSI reporting.

The CSI reception module 1210 may receive at least one of a report withCSI, a request for resources on which to send a CSI report, or signalingthat indicates a change in CSI on resources of the set of reservedresources from a UE, the communicating using a first TTI duration in asystem that supports operation with the first TTI duration and a secondTTI duration that is greater than the first as described with referenceto FIGS. 2-6.

FIG. 13 shows a block diagram 1300 of a base station low latency CSImodule 1110-b which may be a component of a wireless device 1100 or awireless device 1200 that supports low latency PUCCH with SR and CSI inaccordance with various aspects of the present disclosure. The basestation low latency CSI module 1110-b may be an example of aspects of abase station low latency CSI module 1110 described with reference toFIGS. 11-12. The base station low latency CSI module 1110-b may includea UCI resource identification module 1205-a, and a CSI reception module1210-a. Each of these modules may perform the functions described withreference to FIG. 12. The base station low latency CSI module 1110-b mayalso include a reserved resources indication module 1305, a BS RACHmodule 1310, and a resources reassignment module 1315.

The reserved resources indication module 1305 may transmit signalingthat indicates the set of reserved resources to the UE as described withreference to FIGS. 2-6. In some examples, the signaling that indicatesthe set of reserved resources includes a downlink grant.

The BS RACH module 1310 may receive a RACH message from the UE asdescribed with reference to FIGS. 2-6.

The resources reassignment module 1315 may transmit to a different UEsignaling that indicates a reassignment of the reserved resources asdescribed with reference to FIGS. 2-6.

FIG. 14 shows a diagram of a system 1400, including a base station thatsupports low latency PUCCH with SR and CSI in accordance with variousaspects of the present disclosure. System 1400 may include base station105-f, which may be an example of a wireless device 1100, a wirelessdevice 1200, or a base station 105 described with reference to FIGS. 1,2 and 11-13. Base Station 105-f may include a base station low latencyCSI module 1410, which may be an example of a base station low latencyCSI module 1110 described with reference to FIGS. 11-13. Base Station105-f may also include components for bi-directional voice and datacommunications including components for transmitting communications andcomponents for receiving communications. For example, base station 105-fmay communicate bi-directionally with UE 115-h or UE 115-i.

In some cases, base station 105-f may have one or more wired backhaullinks. Base station 105-f may have a wired backhaul link (e.g., S1interface, etc.) to the core network 130. Base station 105-f may alsocommunicate with other base stations 105, such as base station 105-g andbase station 105-h via inter-base station backhaul links (e.g., an X2interface). Each of the base stations 105 may communicate with UEs 115using the same or different wireless communications technologies. Insome cases, base station 105-f may communicate with other base stationssuch as 105-g or 105-h utilizing base station communications module1425. In some examples, base station communications module 1425 mayprovide an X2 interface within an LTE/LTE-A wireless communicationnetwork technology to provide communication between some of the basestations 105. In some examples, base station 105-f may communicate withother base stations through core network 130. In some cases, basestation 105-f may communicate with the core network 130 through networkcommunications module 1430.

The base station 105-f may include a processor 1405, memory 1415(including software (SW) 1420), transceiver 1435, and antenna(s) 1440,which each may be in communication, directly or indirectly, with oneanother (e.g., over bus system 1445). The transceivers 1435 may beconfigured (e.g., in combination with the base station low latency CSImodule 1410) to communicate bi-directionally, via the antenna(s) 1440,with the UEs 115, which may be multi-mode devices. The transceiver 1435(or other components of the base station 105-f) may also be configuredto communicate bi-directionally, via the antennas 1440, with one or moreother base stations (not shown). The transceiver 1435 may include amodem configured to modulate the packets and provide the modulatedpackets to the antennas 1440 for transmission, and to demodulate packetsreceived from the antennas 1440. The base station 105-f may includemultiple transceivers 1435, each with one or more associated antennas1440. The transceiver may be an example of a combined receiver 1105 andtransmitter 1115 of FIG. 11.

The memory 1415 may include RAM and ROM. The memory 1415 may also storecomputer-readable, computer-executable software code 1420 containinginstructions that are configured to, when executed, cause the processor1405 to perform various functions described herein (e.g., low latencyPUCCH with SR and CSI, selecting coverage enhancement techniques, callprocessing, database management, message routing, etc.), including thefunctions described with reference to the base station low latency CSImodule 1410. Alternatively, the software code 1420 may not be directlyexecutable by the processor 1405 but be configured to cause thecomputer, e.g., when compiled and executed, to perform functionsdescribed herein. The processor 1405 may include an intelligent hardwaredevice, e.g., a CPU, a microcontroller, an ASIC, etc. The processor 1405may include various special purpose processors such as encoders, queueprocessing modules, base band processors, radio head controllers,digital signal processor (DSPs), and the like.

The base station communications module 1425 may manage communicationswith other base stations 105. In some cases, a communications managementmodule may include a controller or scheduler for controllingcommunications with UEs 115 in cooperation with other base stations 105.For example, the base station communications module 1425 may coordinatescheduling for transmissions to UEs 115 for various interferencemitigation techniques such as beamforming or joint transmission.

The components of wireless device 700, wireless device 800, low latencyCSI module 710, wireless device 1100, wireless device 1200, base stationlow latency CSI module 1110, UE 115-g, and base station 105-f may,individually or collectively, be implemented with at least oneapplication specific integrated circuit (ASIC) adapted to perform someor all of the applicable functions in hardware. Alternatively, thefunctions may be performed by one or more other processing units (orcores), on at least one IC. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, a fieldprogrammable gate array (FPGA), or another semi-custom IC), which may beprogrammed in any manner known in the art. The functions of each unitmay also be implemented, in whole or in part, with instructions embodiedin a memory, formatted to be executed by one or more general orapplication-specific processors.

FIG. 15 shows a flowchart illustrating a method 1500 for low latencyPUCCH with SR and CSI in accordance with various aspects of the presentdisclosure. The operations of method 1500 may be implemented by a UE 115or its components as described with reference to FIGS. 1-14. Forexample, the operations of method 1500 may be performed by the lowlatency CSI module 710 or low latency CSI module 1010 as described withreference to FIGS. 7-10. In some examples, a UE 115 may execute a set ofcodes to control the functional elements of the UE 115 to perform thefunctions described below. Additionally or alternatively, the UE 115 mayperform aspects the functions described below using special-purposehardware.

At block 1505, the UE 115 may determine CSI for a communication linkthat uses a first TTI duration in a system that supports operation withthe first TTI duration and a second TTI duration that is greater thanthe first as described with reference to FIGS. 2-6. In certain examples,the operations of block 1505 may be performed by the CSI identificationmodule 805 as described with reference to FIG. 8 or the low latency CSImodule 1010 in combination with the transceiver 1035 described withreference to FIG. 10.

At block 1510, the UE 115 may identify resources of an unscheduleduplink channel on which to transmit a report with the determined CSI asdescribed with reference to FIGS. 2-6. Identifying the resources of theunscheduled uplink channel may include selecting the resources from aset of resources reserved for UCI. In some examples, identifying theresources of the unscheduled uplink channel includes determining that aTTI having the first TTI duration is available for CSI reporting. Incertain examples, the operations of block 1510 may be performed by theresource identification module 810 as described with reference to FIG. 8or the low latency CSI module 1010 in combination with the transceiver1035 described with reference to FIG. 10.

At block 1515, the UE 115 may transmit the report on the identifiedresources as described with reference to FIGS. 2-6. The report may betransmitted with a different cyclic shift from an uplink referencesignal. In certain examples, the operations of block 1515 may beperformed by the CSI reporting module 815 as described with reference toFIG. 8 or the low latency CSI module 1010 in combination with thetransceiver 1035 described with reference to FIG. 10.

In some examples, method 1500 includes receiving signaling thatindicates the set of resources reserved for UCI. The signaling may be orinclude a downlink grant. In certain examples, such the operations maybe performed by the transceiver 1035 described with reference to FIG.10. The set of resources reserved for UCI may include resources reservedfor a SR, a CSI report, or HARQ feedback, or any combination thereof.The set of resources reserved for UCI may include a set of resourceblocks of a TTI having the first TTI duration. In some examples, the setof resources reserved for UCI is based at least in part on a number UEsfor which the set of resources reserved for UCI is allocated, and thenumber of UEs may include coherent users or non-coherent users, or both.

FIG. 16 shows a flowchart illustrating a method 1600 for low latencyPUCCH with SR and CSI in accordance with various aspects of the presentdisclosure. The operations of method 1600 may be implemented by a UE 115or its components as described with reference to FIGS. 1-14. Forexample, the operations of method 1600 may be performed by the lowlatency CSI module 710 as described with reference to FIGS. 7-10. Insome examples, a UE 115 may execute a set of codes to control thefunctional elements of the UE 115 to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects thefunctions described below using special-purpose hardware. The method1600 may also incorporate aspects of method 1500 of FIG. 15.

At block 1605, the UE 115 may determine CSI for a communication linkthat uses a first TTI duration in a system that supports operation withthe first TTI duration and a second TTI duration that is greater thanthe first as described with reference to FIGS. 2-6. In certain examples,the operations of block 1605 may be performed by the CSI identificationmodule 805 as described with reference to FIG. 8 or the low latency CSImodule 1010 in combination with the transceiver 1035 as described withreference to FIG. 10.

At block 1610, the UE 115 may identify resources of an unscheduleduplink channel on which to transmit a report with the determined CSI asdescribed with reference to FIGS. 2-6. In some cases, identifying theresources of the unscheduled uplink channel includes selecting theresources from a set of resources reserved for UCI. In certain examples,the operations of block 1610 may be performed by the resourceidentification module 810 as described with reference to FIG. 8 or thelow latency CSI module 1010 in combination with the transceiver 1035 asdescribed with reference to FIG. 10.

At block 1615, the UE 115 may transmit the report on the identifiedresources as described with reference to FIGS. 2-6. In certain examples,the operations of block 1615 may be performed by the CSI reportingmodule 815 as described with reference to FIG. 8 or the low latency CSImodule 1010 in combination with the transceiver 1035 as described withreference to FIG. 10.

At block 1620, the UE 115 may receive signaling that indicates the setof reserved resources as described with reference to FIGS. 2-6. Incertain examples, the operations of block 1620 may be performed by thereceiver 705 as described with reference to FIG. 7 or 8 or the lowlatency CSI module 1010 in combination with the transceiver 1035 asdescribed with reference to FIG. 10.

FIG. 17 shows a flowchart illustrating a method 1700 for low latencyPUCCH with SR and CSI in accordance with various aspects of the presentdisclosure. The operations of method 1700 may be implemented by a UE 115or its components as described with reference to FIGS. 1-14. Forexample, the operations of method 1700 may be performed by the lowlatency CSI module 710 as described with reference to FIGS. 7-10. Insome examples, a UE 115 may execute a set of codes to control thefunctional elements of the UE 115 to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects thefunctions described below using special-purpose hardware. The method1700 may also incorporate aspects of methods 1500 and 1600 of FIGS. 15and 16.

At block 1705, the UE 115 may determine CSI for a communication linkthat uses a first TTI duration in a system that supports operation withthe first TTI duration and a second TTI duration that is greater thanthe first as described with reference to FIGS. 2-6. In certain examples,the operations of block 1705 may be performed by the CSI identificationmodule 805 as described with reference to FIG. 8. or the low latency CSImodule 1010 in combination with the transceiver 1035 as described withreference to FIG. 10.

At block 1710, the UE 115 may identify resources of an unscheduleduplink channel on which to transmit a report with the determined CSI asdescribed with reference to FIGS. 2-6. In certain examples, theoperations of block 1710 may be performed by the resource identificationmodule 810 as described with reference to FIG. 8. or the low latency CSImodule 1010 in combination with the transceiver 1035 as described withreference to FIG. 10.

At block 1715, the UE 115 may transmit the report on the identifiedresources as described with reference to FIGS. 2-6. In certain examples,the operations of block 1715 may be performed by the CSI reportingmodule 815 as described with reference to FIG. 8 or the low latency CSImodule 1010 in combination with the transceiver 1035 as described withreference to FIG. 10.

At block 1720, the UE 115 may transmit a RACH message as described withreference to FIGS. 2-6. In certain examples, the operations of block1720 may be performed by the RACH module 905 as described with referenceto FIG. 9 or the low latency CSI module 1010 in combination with thetransceiver 1035 as described with reference to FIG. 10.

At block 1725, the UE 115 may receive a message responsive to the RACHmessage, such that the resources of the unscheduled uplink channel areidentified based on the responsive message as described with referenceto FIGS. 2-6. In certain examples, the operations of block 1725 may beperformed by the RACH module 905 as described with reference to FIG. 9or the low latency CSI module 1010 in combination with the transceiver1035 as described with reference to FIG. 10.

FIG. 18 shows a flowchart illustrating a method 1800 for low latencyPUCCH with SR and CSI in accordance with various aspects of the presentdisclosure. The operations of method 1800 may be implemented by a UE 115or its components as described with reference to FIGS. 1-14. Forexample, the operations of method 1800 may be performed by the lowlatency CSI module 710 as described with reference to FIGS. 7-10. Insome examples, a UE 115 may execute a set of codes to control thefunctional elements of the UE 115 to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects thefunctions described below using special-purpose hardware. The method1800 may also incorporate aspects of methods 1500, 1600, and 1700 ofFIGS. 15-17.

At block 1805, the UE 115 may determine CSI for a communication linkthat uses a first TTI duration in a system that supports operation withthe first TTI duration and a second TTI duration that is greater thanthe first as described with reference to FIGS. 2-6. In certain examples,the operations of block 1805 may be performed by the CSI identificationmodule 805 as described with reference to FIG. 8 or the low latency CSImodule 1010 in combination with the transceiver 1035 as described withreference to FIG. 10.

At block 1810, the UE 115 may transmit a request for resources on whichto send a report with the determined CSI as described with reference toFIGS. 2-6. In certain examples, the operations of block 1810 may beperformed by the resource request module 910 as described with referenceto FIG. 9 or the low latency CSI module 1010 in combination with thetransceiver 1035 as described with reference to FIG. 10.

At block 1815, the UE 115 may receive a grant for uplink resources forthe report in response to the request as described with reference toFIGS. 2-6. In certain examples, the operations of block 1815 may beperformed by the resource grant module 915 as described with referenceto FIG. 9 or the low latency CSI module 1010 in combination with thetransceiver 1035 as described with reference to FIG. 10.

At block 1820, the UE 115 may transmit the report using the uplinkresources as described with reference to FIGS. 2-6. In certain examples,the operations of block 1820 may be performed by the CSI reportingmodule 815 as described with reference to FIG. 8 or the low latency CSImodule 1010 in combination with the transceiver 1035 as described withreference to FIG. 10.

FIG. 19 shows a flowchart illustrating a method 1900 for low latencyPUCCH with SR and CSI in accordance with various aspects of the presentdisclosure. The operations of method 1900 may be implemented by a UE 115or its components as described with reference to FIGS. 1-14. Forexample, the operations of method 1900 may be performed by the lowlatency CSI module 710 as described with reference to FIGS. 7-10. Insome examples, a UE 115 may execute a set of codes to control thefunctional elements of the UE 115 to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects thefunctions described below using special-purpose hardware. The method1900 may also incorporate aspects of methods 1500, 1600, 1700, and 1800of FIGS. 15-18.

At block 1905, the UE 115 may transmit a report with CSI for acommunication link that uses a first TTI duration in a system thatsupports operation with the first TTI duration and a second TTI durationthat is greater than the first as described with reference to FIGS. 2-6.In certain examples, the operations of block 1905 may be performed bythe CSI reporting module 815 as described with reference to FIG. 8 orthe low latency CSI module 1010 in combination with the transceiver 1035as described with reference to FIG. 10.

At block 1910, the UE 115 may determine a change in a channel state forthe communication link as described with reference to FIGS. 2-6. Incertain examples, the operations of block 1910 may be performed by thechannel state difference module 920 as described with reference to FIG.9 or the low latency CSI module 1010 in combination with the transceiver1035 as described with reference to FIG. 10.

At block 1915, the UE 115 may transmit signaling that indicates adifference between the reported CSI and the change in the channel stateas described with reference to FIGS. 2-6. In certain examples, theoperations of block 1915 may be performed by the difference reportingmodule 925 as described with reference to FIG. 9 or the low latency CSImodule 1010 in combination with the transceiver 1035 as described withreference to FIG. 10.

In some examples of the method 1900, the report with the CSI or thesignaling that indicates the difference between the CSI and the changein the channel state is transmitted on resources selected from a set ofresources reserved for UCI. The set of resources reserved for UCI mayinclude resources reserved for SR, CSI reports, HARQ feedback, or anycombination thereof. The set of resources reserved for UCI may bereserved based at least in part on a number of UEs for which the set ofresources reserved for UCI is allocated, and the number of UEs mayinclude coherent users or non-coherent users, or both. The report withthe CSI or the signaling that indicates the difference between the CSIand the change in the channel state is transmitted with a differentcyclic shift from an uplink reference signal.

Method 1900 may also include receiving a grant for resources on which tosend the report with the CSI or the signaling that indicates thedifference between the CSI and the change in the channel state in adownlink data channel. In certain examples, such the operations may beperformed by the transceiver 1035 as described with reference to FIG.10.

FIG. 20 shows a flowchart illustrating a method 2000 for low latencyPUCCH with SR and CSI in accordance with various aspects of the presentdisclosure. The operations of method 2000 may be implemented by a basestation 105 or its components as described with reference to FIGS. 1-14.For example, the operations of method 2000 may be performed by the basestation low latency CSI module 1110 as described with reference to FIGS.11-14. In some examples, a base station 105 may execute a set of codesto control the functional elements of the base station 105 to performthe functions described below. Additionally or alternatively, the basestation 105 may perform aspects the functions described below usingspecial-purpose hardware.

At block 2005, the base station 105 may determine a set of resourcesreserved for UCI as described with reference to FIGS. 2-6. In certainexamples, the operations of block 2005 may be performed by the UCIresource identification module 1205 as described with reference to FIG.12 or the base station low latency CSI module 1410 in combination withthe transceiver 1435 as described with reference to FIG. 14.

At block 2010, the base station 105 may receive at least one of a reportwith CSI, a request for resources on which to send a CSI report, orsignaling that indicates a change in CSI on resources of the set ofreserved resources from a UE, and the receive may include receive usinga first TTI duration in a system that supports operation with the firstTTI duration and a second TTI duration that is greater than the first asdescribed with reference to FIGS. 2-6. In certain examples, theoperations of block 2010 may be performed by the CSI reception module1210 as described with reference to FIG. 12 or the base station lowlatency CSI module 1410 in combination with the transceiver 1435 asdescribed with reference to FIG. 14.

Thus, methods 1500, 1600, 1700, 1800, 1900, and 2000 may provide for lowlatency PUCCH with SR and CSI. It should be noted that methods 1500,1600, 1700, 1800, 1900, and 2000 describe possible implementation, andthat the operations and the steps may be rearranged or otherwisemodified such that other implementations are possible. In some examples,aspects from two or more of the methods 1500, 1600, 1700, 1800, 1900,and 2000 may be combined.

The description herein provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the scope of the disclosure. Various examples may omit,substitute, or add various procedures or components as appropriate.Also, features described with respect to some examples may be combinedin other examples.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.The terms “system” and “network” are often used interchangeably. A codedivision multiple access (CDMA) system may implement a radio technologysuch as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc.CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0and A are commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856)is commonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data(HRPD), etc. UTRA includes Wideband CDMA (WCDMA) and other variants ofCDMA. A time division multiple access (TDMA) system may implement aradio technology such as Global System for Mobile Communications (GSM).An OFDMA system may implement a radio technology such as Ultra MobileBroadband (UMB), Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part ofUniversal Mobile Telecommunications system (UMTS). 3GPP Long TermEvolution (LTE) and LIE-Advanced (LTE-A) are new releases of UniversalMobile Telecommunications System (UMTS) that use E-UTRA. UTRA, E-UTRA,Universal Mobile Telecommunications System (UMTS), LIE, LTE-A, andGlobal System for Mobile communications (GSM) are described in documentsfrom an organization named “Third Generation Partnership Project”(3GPP). CDMA2000 and UMB are described in documents from an organizationnamed “3rd Generation Partnership Project 2” (3GPP2). The techniquesdescribed herein may be used for the systems and radio technologiesmentioned above as well as other systems and radio technologies. Thedescription herein, however, describes an LTE system for purposes ofexample, and LTE terminology is used in much of the description above,although the techniques are applicable beyond LTE applications.

In LTE/LTE-A networks, including such networks described herein, theterm evolved node B (eNB) may be generally used to describe the basestations. The wireless communications system or systems described hereinmay include a heterogeneous LTE/LTE-A network in which different typesof evolved node B (eNBs) provide coverage for various geographicalregions. For example, each eNB or base station may provide communicationcoverage for a macro cell, a small cell, or other types of cell. Theterm “cell” is a 3GPP term that can be used to describe a base station,a carrier or component carrier associated with a base station, or acoverage area (e.g., sector, etc.) of a carrier or base station,depending on context.

Base stations may include or may be referred to by those skilled in theart as a base transceiver station, a radio base station, an accesspoint, a radio transceiver, a NodeB, eNodeB (eNB), Home NodeB, a HomeeNodeB, or some other suitable terminology. The geographic coverage areafor a base station may be divided into sectors making up a portion ofthe coverage area. The wireless communications system or systemsdescribed herein may include base stations of different types (e.g.,macro or small cell base stations). The UEs described herein may be ableto communicate with various types of base stations and network equipmentincluding macro eNBs, small cell eNBs, relay base stations, and thelike. There may be overlapping geographic coverage areas for differenttechnologies.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell is alower-powered base station, as compared with a macro cell, that mayoperate in the same or different (e.g., licensed, unlicensed, etc.)frequency bands as macro cells. Small cells may include pico cells,femto cells, and micro cells according to various examples. A pico cell,for example, may cover a small geographic area and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A femto cell may also cover a small geographic area (e.g., ahome) and may provide restricted access by UEs having an associationwith the femto cell (e.g., UEs in a closed subscriber group (CSG), UEsfor users in the home, and the like). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a small cell may be referred toas a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB maysupport one or multiple (e.g., two, three, four, and the like) cells(e.g., component carriers). A UE may be able to communicate with varioustypes of base stations and network equipment including macro eNBs, smallcell eNBs, relay base stations, and the like.

The wireless communications system or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations may have similar frame timing, andtransmissions from different base stations may be approximately alignedin time. For asynchronous operation, the base stations may havedifferent frame timing, and transmissions from different base stationsmay not be aligned in time. The techniques described herein may be usedfor either synchronous or asynchronous operations.

The downlink transmissions described herein may also be called forwardlink transmissions while the uplink transmissions may also be calledreverse link transmissions. Each communication link describedherein—including, for example, wireless communications system 100 and200 of FIGS. 1 and 2—may include one or more carriers, where eachcarrier may be a signal made up of multiple sub-carriers (e.g., waveformsignals of different frequencies). Each modulated signal may be sent ona different sub-carrier and may carry control information (e.g.,reference signals, control channels, etc.), overhead information, userdata, etc. The communication links described herein (e.g., communicationlinks 125 of FIG. 1) may transmit bidirectional communications usingfrequency division duplex (FDD) (e.g., using paired spectrum resources)or time division duplex (TDD) operation (e.g., using unpaired spectrumresources). Frame structures may be defined for frequency divisionduplex (FDD) (e.g., frame structure type 1) and TDD (e.g., framestructure type 2).

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general-purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a digital signal processor (DSP) and a microprocessor, multiplemicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more of”) indicates an inclusivelist such that, for example, a list of at least one of A, B, or C meansA or B or C or AB or AC or BC or ABC (i.e., A and B and C).

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media caninclude RAM, ROM, electrically erasable programmable read only memory(EEPROM), compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave are included in the definition of medium. Disk and disc,as used herein, include CD, laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

All structural and functional equivalents to the elements of the variousaspects described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. The words “module,” “mechanism,”“element,” “device,” “component,” and the like may not be a substitutefor the word “means.” As such, no claim element is to be construed as ameans plus function unless the element is expressly recited using thephrase “means for.”

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notto be limited to the examples and designs described herein but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method of wireless communication, comprising:determining channel state information (CSI) for a communication linkthat uses a first transmission time interval (TTI) duration in a systemthat supports operation with the first TTI duration and a second TTIduration that is greater than the first TTI duration; identifyingresources of an unscheduled uplink channel on which to transmit a reportwith the determined CSI; and transmitting the report on the identifiedresources.
 2. The method of claim 1, wherein identifying the resourcesof the unscheduled uplink channel comprises: selecting the resourcesfrom a set of resources reserved for uplink control information (UCI).3. The method of claim 2, further comprising: receiving signaling thatindicates the set of resources reserved for UCI.
 4. The method of claim3, wherein the signaling comprises a downlink grant.
 5. The method ofclaim 2, wherein the set of resources reserved for UCI comprisesresources reserved for a scheduling request (SR), a CSI report, orhybrid automatic repeat request (HARQ) feedback, or any combinationthereof.
 6. The method of claim 2, wherein the set of resources reservedfor UCI comprises a set of resource blocks of a TTI having the first TTIduration.
 7. The method of claim 2, wherein the set of resourcesreserved for UCI is based at least in part on a number of user equipment(UEs) for which the set of resources reserved for UCI is allocated, andwherein the number of UEs comprises coherent users or non-coherentusers, or both.
 8. The method of claim 1, wherein identifying theresources of the unscheduled uplink channel comprises: determining thata TTI having the first TTI duration is available for CSI reporting. 9.The method of claim 1, wherein the report is transmitted with adifferent cyclic shift from an uplink reference signal.
 10. A method ofwireless communication, comprising: transmitting a report with channelstate information (CSI) for a communication link that uses a firsttransmission time interval (TTI) duration in a system that supportsoperation with the first TTI duration and a second TTI duration that isgreater than the first; determining a change in a channel state for thecommunication link; and transmitting signaling that indicates adifference between the CSI and the change in the channel state.
 11. Themethod of claim 10, wherein the report with the CSI or the signalingthat indicates the difference between the CSI and the change in thechannel state is transmitted on resources selected from a set ofresources reserved for uplink control information (UCI).
 12. The methodof claim 11, wherein the set of resources reserved for UCI comprisesresources reserved for scheduling request (SR), CSI reports, hybridautomatic repeat request (HARQ) feedback, or any combination thereof.13. The method of claim 11, wherein the set of resources reserved forUCI is reserved based at least in part on a number of user equipment(UEs) for which the set of resources reserved for UCI is allocated, andwherein the number of UEs comprises coherent users or non-coherentusers, or both.
 14. The method of claim 10, further comprising:receiving a grant for resources on which to send the report with the CSIor the signaling that indicates the difference between the CSI and thechange in the channel state in a downlink data channel.
 15. The methodof claim 10, wherein the report with the CSI or the signaling thatindicates the difference between the CSI and the change in the channelstate is transmitted with a different cyclic shift from an uplinkreference signal.
 16. An apparatus for wireless communication,comprising: a processor; memory in electronic communication with theprocessor; and instructions stored in the memory and operable, whenexecuted by the processor, to cause the apparatus to: determine channelstate information (CSI) for a communication link that uses a firsttransmission time interval (TTI) duration in a system that supportsoperation with the first TTI duration and a second TTI duration that isgreater than the first TTI duration; identify resources of anunscheduled uplink channel on which to transmit a report with thedetermined CSI; and transmit the report on the identified resources. 17.The apparatus of claim 16, wherein the instructions are operable tocause the apparatus to: select the resources from a set of resourcesreserved for uplink control information (UCI).
 18. The apparatus ofclaim 17, wherein the instructions are operable to cause the apparatusto: receive signaling that indicates the set of resources reserved forUCI.
 19. The apparatus of claim 18, wherein the signaling comprises adownlink grant.
 20. The apparatus of claim 17, wherein the set ofresources reserved for UCI comprises resources reserved for an SR, a CSIreport, or hybrid automatic repeat request (HARQ) feedback, or anycombination thereof.
 21. The apparatus of claim 17, wherein the set ofresources reserved for UCI comprises a set of resource blocks of a TTIhaving the first TTI duration.
 22. The apparatus of claim 17, whereinthe set of resources reserved for UCI is based at least in part on anumber of user equipment (UEs) for which the set of resources reservedfor UCI is allocated, and wherein the number of UEs comprises coherentusers or non-coherent users, or both.
 23. The apparatus of claim 16,wherein the instructions operable to cause the apparatus to: determinethat a TTI having the first TTI duration is available for CSI reporting.24. The apparatus of claim 16, wherein the instructions are operable tocause the apparatus to: transmit the report with a different cyclicshift from an uplink reference signal.
 25. An apparatus for wirelesscommunication, comprising: a processor; memory in electroniccommunication with the processor; and instructions stored in the memoryand operable, when executed by the processor, to cause the apparatus to:transmit a report with channel state information (CSI) for acommunication link that uses a first transmission time interval (TTI)duration in a system that supports operation with the first TTI durationand a second TTI duration that is greater than the first; and determinea change in a channel state for the communication link; and transmitsignaling that indicates a difference between the CSI and the change inthe channel state.
 26. The apparatus of claim 25, wherein the reportwith the CSI or the signaling that indicates the difference betweenreported CSI and the change in the channel state is transmitted onresources selected from a set of resources reserved for uplink controlinformation (UCI).
 27. The apparatus of claim 26, wherein the set ofresources reserved for UCI comprises resources reserved for schedulingrequest (SR), CSI reports, hybrid automatic repeat request (HARQ)feedback, or any combination thereof.
 28. The apparatus of claim 26,wherein the set of resources reserved for UCI is reserved based at leastin part on a number of user equipment (UEs) for which the set ofresources reserved for UCI is allocated, and wherein the number of UEscomprises coherent users or non-coherent users, or both.
 29. Theapparatus of claim 25, wherein the instructions are operable to causethe apparatus to: receive a grant for resources on which to send thereport with the CSI or the signaling that indicates the differencebetween the CSI and the change in the channel state in a downlink datachannel.
 30. The apparatus of claim 25, wherein the report with the CSIor the signaling that indicates the difference between the CSI and thechange in the channel state is transmitted with a different cyclic shiftfrom an uplink reference signal.